Time-resolved contrast imaging for lidar

ABSTRACT

A system and method of LIDAR imaging to overcome scattering effects pulses a scene with light pulse sequences from a light source. Reflected light from the scene is measured for each light pulse to form a sequence of time-resolved signals. Time-resolved contrast is calculated for each location in a scene. A three-dimensional map or image of the scene is created from the time-resolved contrasts. The three-dimensional map is then utilized to affect operation of a vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/280,723 filed Feb. 20, 2019, now allowed, which, in turn, claims thebenefit of U.S. provisional application Ser. No. 62/632,917 filed Feb.20, 2018, the disclosures of which are hereby incorporated in theirentirety by reference herein.

TECHNICAL FIELD

The present invention relates to light detection and ranging (LIDAR)three-dimensional imaging, particularly for use in scatteringenvironments, and more particularly for use with autonomous andnon-autonomous vehicles.

BACKGROUND

The demand for LIDAR imaging solutions has increased with the advent ofautonomous vehicles and drones. LIDAR uses a pulsed laser orlight-emitting diode (LED) beam to probe the distance to a reflector bymeasuring the time it takes for the light to be reflected back to thedevice. This allows for very precise measurements of a givenenvironment. However, the small wavelength of light means thatconventional LIDAR systems fail in conditions such as rain, fog, orsmoke. This is because the pulsed laser or LED light is scattered byrain drops, smoke, sand, or other scatterers. Even though most of thelight is scattered in the forward direction, some of it reflects backtoward the LIDAR sensor. As a result, the LIDAR sensor provides a falsereading representing the distance to the droplet or smoke particle, notto the object behind it.

To address the scattering problem, time filtering of LIDAR returnsignals has been tried to remove the effect of early scattered photons(time-gated LIDAR). In time-gated LIDAR, the return light signal is onlyanalyzed in gated intervals to reduce effects from intervening scatter.Scattered photons are removed to the extent they arrive in the periodbetween gated intervals. However, this technique is time consuming,provides lower resolution, and cannot operate in challengingenvironmental conditions. Improved high-resolution sensing techniquesthat can be effectively used in challenging environmental conditions andthat are fast enough to be used in autonomous vehicles are needed.

SUMMARY

The deficiencies of the prior art are remedied by a LIDAR system andmethod that can be effectively used in vehicles such as, but not limitedto, cars, trucks, autonomous vehicles, drones, planes, trains, and shipsunder challenging environmental conditions. In accordance with oneembodiment of the invention, a LIDAR system is provided comprising alaser or LED light source, transmitter optics, and receiver optics. Thesystem is arranged to produce a sequence of light pulses from the lightsource. The transmitter optics directs the light pulses from the sourcetoward a scene. Light reflected from the scene in a time period betweenpulses is received in the receiver optics. The optics converts the lightinto a time-resolved signal for reflected light produced by each of thelight pulses. An integrated circuit, such as may be found in a computerprocesser or an application-specific integrated circuit (ASIC), isconfigured to calculate a time-resolved contrast over the plurality oftime-resolved signals produced by the plurality of light pulses in nearreal-time.

By producing a time-resolved contrast for each location in the scene,during a scanning process, a contrast image can be created for theentire scene. Objects that would be otherwise obscured due to scatterfrom environmental inferences such as fog, rain, sand, or smoke are madevisible in the contrast image. Indeed, the time resolution provides athree-dimensional image or map and permits detection of the distance toan object.

In an embodiment of the invention, contrast is calculated by dividingthe standard deviation of signals at a given time position across eachof the plurality of time-resolved signals by the mean of the signals atthe given time position across each of the plurality of time-resolvedsignals. Alternatively, contrast can be calculated by dividing thesquare of the standard deviation by the square of the mean. Further, acorrection for shot noise can be achieved by calculating the differenceof the square of the standard deviation and the mean, and dividing thedifference by the square of the mean. The time position of the absolutemaximum or absolute minimum of the time-resolved contrast may thencorrespond to the distance to an object. In an embodiment, thesecalculations may take place in a sliding window on the time-resolvedsignals to reduce the number of calculations necessary.

In some embodiments, the transmitter optics may be arranged to spreadthe light pulses so as to flood-illuminate the scene, a process known asflash LIDAR.

In accordance with a corresponding method embodiment of the invention, aprocess is repeated at each of a plurality of locations in the scenebeing scanned. A sequence of light pulses is transmitted toward a givenlocation. Between consecutive pulses, reflected light is received fromthe scene in the time period between the pulses to produce atime-resolved signal. Contrast over a plurality of the time-resolvedsignals is calculated to produce a time-resolved contrast signal for thegiven location. Repeating the process at all locations in a sceneproduces time-resolved contrast signals throughout the scene. These maybe used to determine distance to objects in the scene, to create athree-dimensional map of the scene, or to provide an image in whichobjects in the scene are visible despite scattering effects due toenvironmental factors or other scatterers. Instructions for thiscalculation may reside in a program code in a computer processor, oralternatively, may be implemented in an ASIC or other dedicatedprocessor.

In accordance with an alternative embodiment of the invention , lightpulses are transmitted at each of a plurality of locations in the sceneto be scanned. A sensor receives reflected light from the scene in atime period between pulses. The sensor produces a signal as a functionof time for the light pulse transmitted to each location. For each givenlocation, time-resolved contrast is calculated over a plurality ofsignals produced for locations in a vicinity of the given location. Toproduce a time-resolved contrast image for the scene, the LIDAR systemscans the scene, typically in a raster scan. Each location is orientedat a pan angle and a tilt angle relative to the LIDAR system.

The time-resolved contrast calculations involve calculating a standarddeviation of the signals at a given time position produced for locationsin the vicinity of a given location. A mean is calculated for thesignals at the given time position produced for the locations in thevicinity of the given location . The time-resolved contrast is thestandard deviation divided by the mean or, alternatively, the square ofthe standard deviation divided by the square of the mean. This isrepeated for all the given locations in the scene. As with the otherdescribed embodiments, objects in the scene may be detected and/ordistances to an object can be determined from the time-resolvedcontrast. A three-dimensional map and/or image of the scene may also becreated. Optionally, flash LIDAR may be used with this method as well.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of embodiments will be more readily understood byreference to the following detailed description, taken with reference tothe accompanying drawings, in which:

FIG. 1 shows a typical environment for embodiments of the presentinvention;

FIG. 2 shows various logical steps in a method for operating a LIDARsystem in a vehicle to overcome scattering effects according to anembodiment of the present invention;

FIG. 3 shows various logical steps in a method for time-resolvedcontrast LIDAR imaging according to an embodiment of the presentinvention;

FIG. 4 shows various logical steps in a method for time-resolvedcontrast LIDAR imaging with shot noise correction according to anembodiment of the present invention;

FIG. 5 shows various logical steps in a method for time-resolvedcontrast LIDAR imaging according to an alternative embodiment of thepresent invention; and

FIG. 6 shows various logical steps in a method for time-resolvedcontrast LIDAR imaging according to an alternative embodiment of thepresent invention.

DETAILED DESCRIPTION

Definitions. As used in this description and the accompanying claims,the following term shall have the meaning indicated, unless the contextotherwise requires:

Vehicle: any manned or unmanned vehicle such as, but not limited to,cars, trucks, autonomous vehicles, rovers, unmanned ground vehicles(UGVs), unmanned aerial vehicles (UAVs), drones, aircraft, spacecraft,rail-based vehicles, trains, boats, ships, unmanned surface vehicles(USVs), unmanned underwater vehicles (UUVs).

FIG. 1 depicts a LIDAR system in a typical environment for embodimentsof the present invention. LIDAR system 100 may be used in a vehicle. TheLIDAR system 100 may comprise a light source 101 and transmitter optics102. Exemplarily, the light source 101 may be a laser or it may be alight-emitting diode (LED). The light source 101 may emit pulsed lightdirected at a scene. The transmitter optics 102 allows the LIDAR system100 to steer the output of the light source 101 toward a desiredlocation. The output of the transmitter optics 102 is a pulsed lightbeam 103 that is directed at a location in the scene. For example, thelocation could be a scanning location in the scene. The scanninglocation may be determined such that the entire scene can be scannedusing N scanning locations. Alternatively, the transmitter optics 102may be configured to spread the output of the light source 101 so as toflood-illuminate the whole scene.

For example , the pulsed light beam 103 may be directed at an object 106that is in view of the LIDAR system 100. The pulsed light beam 103 maytravel along transmission path 104 toward the object 106. Ideally, thetransmission path 104 would be clear dry air, but in reality thetransmission path 104 may be obscured by optical scatterers 105,including, but not limited to, fog, rain, smoke, or sand. The object 106may be located behind the optical scatterers 105 and may therefore notbe easily visible to the naked eye or to a LIDAR system as known in theprior art.

The pulsed light beam 103 traveling along the path transmission 104 maybe reflected by any number of the optical scatterers 105 (reflection notshown) and/or off the object 106. When reflected off the object 106, thelight may travel back to the LIDAR system 100 along reflection path 107.Again, ideally the reflection path 107 would be clear dry air, but itmay be obscured by optical scatterers 105. The portion of the light notobscured by optical scatterers 105 reaches the LIDAR system 100 asreflected light 108. Receiver optics 109, arranged to receive and detectthe reflected light 108 from the scene, may then produce a time-resolvedsignal in accordance with the intensity and timing of the reflectedlight 108. Since the light beam 103 is pulsed, the receiver optics 109may be configured to receive the reflected light 108 in a time periodbetween light pulses. The receiver optics 109 may also use an opticalfilter to isolate light from the pulsed source 101. The plurality oftime-resolved signals may then be passed on to an integrated circuit110.

The integrated circuit 110 may be part of the LIDAR system 100. Theintegrated circuit 110 may be configured to calculate a time-resolvedcontrast for each of the plurality of time-resolved signals receivedfrom the receiver optics 109 to determine the distance to the targetfrom the time position of an absolute maximum or minimum along thetime-resolved contrast. Exemplarily, the integrated circuit 110 may bean application-specific integrated circuit (ASIC) or it may be aprocessor including program code. The integrated circuit 110 may also beany other kind of circuit configured to calculate a time-resolvedcontrast in accordance with the embodiments of this invention asdescribed in more detail in reference to FIGS. 2-6 . The scanningprocess may be repeated N times for N scanning locations in the scene.

The LIDAR system 100 may further comprise an integrated circuitconfigured to generate a three-dimensional map of the scene from aplurality of time-resolved contrasts, such as the time-resolvedcontrasts corresponding to the N scanning locations. This integratedcircuit may be the same as the integrated circuit 110, or it may be adifferent integrated circuit (not shown). Types of integrated circuitscontemplated include , but are not limited to, ASICs or processorsincluding program code. The integrated circuit may receive a pluralityof time-resolved contrasts corresponding to a plurality of locations inthe scene (e.g., the N scanning locations). From the time-resolvedcontrast for each scanning location, the integrated circuit may generatea three-dimensional map of the scene. Exemplarily, the integratedcircuit may detect the time position of the absolute maximum or minimumof the time-resolved contrast. The time position at the maximum orminimum corresponds to the distance to an object at the location in thescene corresponding to that time-resolved contrast. The integratedcircuit may then generate a three-dimensional map from the detecteddistances.

Exemplarily, the three-dimensional map of the scene may be utilized toaffect the operation of an autonomous vehicle as known to a personhaving skill in the art and, for example, described in U.S. Pat. No.8,761,990, which is incorporated herein by reference in its entirety.Alternatively, the three-dimensional map of the scene may be utilized toaid a driver of a vehicle with driving in challenging environmentalconditions. A display 111 may be coupled to the LIDAR system 100. Thedisplay 111 may also be coupled to a camera 113. The display 111 mayshow a visual image produced by the camera 113. The visual image may,for example, be a real-time visual image of the road in front of thevehicle. The display 111 may further be configured to superimpose thethree-dimensional map generated by the LIDAR system 100 on the visualimage produced by the camera 113. The superimposition 112 of the visualimage and the three-dimensional map may help the driver of the vehicledetect objects in front of the vehicle. For example, the superimposition112 may show grey fog as recorded by the camera 113 superimposed with athree-dimensional LIDAR map depicting an outline of an oncoming vehicle.

FIG. 2 shows various logical steps in a method 200 for operating a LIDARsystem 100 in a vehicle to overcome scattering effects according to anembodiment of the present invention. Specifically, the procedure startsat step 210 and proceeds to step 220 where a sequence of light pulsesare transmitted towards one of a plurality of locations in a scene(e.g., one of the N scanning locations). The light pulses may originatefrom a light source 101, including, but not limited to, a laser or anLED light source. The light pulses may further be transmitted bytransmitter optics 102 which may direct the light pulses towards apredetermined location. The transmitter optics 102 may alternativelyspread the light pulses so as to flash-illuminate the whole scene.

The method then proceeds to step 230 where light reflected from thescene is received. The reflected light may be received by receiveroptics 109. More specifically, the receiver optics 109 may receive thereflected light in time period between light pulses to produce atime-resolved signal between each of consecutive light pulses. Theplurality of time-resolved signals produced by the receiver optics 109for the one location is then passed on to an integrated circuit 110.

In step 240, the integrated circuit 110 calculates a time-resolvedcontrast for the one of a plurality of locations (e.g., one of the Nscanning locations) from the plurality of time-resolved signals for thatlocation as received from the receiver optics 109. Types of integratedcircuits contemplated include, but are not limited to, ASICs or computerprocessors including instructions for calculating the time-resolvedcontrast. The integrated circuit 110 may calculate the time-resolvedcontrast as described in detail below in reference to FIGS. 3 and 4 .

The procedure moves on to step 250 where the LIDAR system 100 determineswhether a time-resolved contrast has been calculated for each one of theplurality of locations (e.g., each one of the N scanning locations in ascene). If a time-resolved contrast has not been calculated for alllocations, the procedure goes back to step 220 to calculate the time-resolved contrast for another one of the plurality of locations. If atime-resolved contrast has been calculated for all locations, theprocedure moves on to step 260.

At step 260, the LIDAR system 100 generates a three-dimensional map ofthe scene from the plurality of time-resolved contrasts calculated forthe plurality of locations. The map may be generated by the integratedcircuit 110, or it may be generated by another integrated circuit. Themap may, for example, be generated by detecting the time position of theabsolute maximum or minimum of each time-resolved contrast. The timeposition at the maximum or minimum corresponds to the distance to anobject at the location in the scene corresponding to that time-resolvedcontrast. Having calculated such distance for each location in a scene,the LIDAR system 100 may detect an object in the scene from thedistances as reflected in the three-dimensional map of the scene.

The procedure then moves on to step 270 where the generatedthree-dimensional map is utilized to affect operation of the vehicle.The utilizing may comprise displaying the generated map on a display 111superimposed on a visual image produced by a camera 113. Thesuperimposition 112 may aid a driver of a vehicle in recognizing objectsin front of the vehicle that would otherwise be invisible due tochallenging environmental conditions. For example, the superimposition112 may allow the driver to see an oncoming vehicle in dense fog. Theutilizing may further comprise using the generated three-dimensional mapto affect the operation of an autonomous vehicle as known to a personhaving skill in the art and, for example, contemplated in U.S. Pat. No.8,761,990. The procedure then ends at step 280.

FIG. 3 shows various logical steps in method 300 for calculatingtime-resolved contrast in accordance with an embodiment of thisinvention. The procedure starts at step 310 and moves on to step 320where the integrated circuit 110 calculates a standard deviation of thetime-resolved signals at each given time position over the plurality oftime-resolved signals received from the receiver optics 109. At step330, the integrated circuit 110 calculates a mean of the time-resolvedsignals at each given time position over the plurality of time-resolvedsignals. The method proceeds to step 340 where the integrated circuit110 divides, at each given time position, the standard deviation of thetime-resolved signals by the mean of the time-resolved signals. Theresult of this division is the time-resolved contrast. The procedureends at step 350. While FIG. 3 depicts calculating the standarddeviation and mean, the integrated circuit 110 may alternativelycalculate the square of the standard deviation and divide it by thesquare of the mean. Further , while FIG. 3 shows calculations on theentire time-resolved signal, it is expressly contemplated that thecalculations may be performed on a sliding time window on each of theplurality of time-resolved signals. This may reduce the number ofcalculations needed to determine the time position of the absolutemaximum or minimum of the time-resolved contrast at a given location bytaking into account the time positions of the absolute maxima or minimain the vicinity of the given location. For example, instead ofperforming calculations for all time positions, the integrated circuit110 may only calculate the time-resolved contrast in a limited timewindow corresponding to the time position of the absolute maximum orminimum of the time-resolved contrast in the vicinity of the givenlocation.

FIG. 4 shows various logical steps in method 400 for calculatingtime-resolved contrast corrected for shot noise in accordance with analternative embodiment of this invention. Shot noise is associated withthe particle nature of light and describes the fluctuations of thenumber of photons detected due to their occurrence independent of eachother, causing fluctuations in amplitude of the time-resolved signals.The procedure starts at step 410 and moves on to step 420 where theintegrated circuit 110 calculates a square of a standard deviation ofthe time-resolved signals at each given time position over the pluralityof time-resolved signals received from the receiver optics 109.

The method then proceeds to step 430 where the integrated circuit 110calculates a mean of the time-resolved signals at each given timeposition over the plurality of time-resolved signals. At step 440, theintegrated circuit 110 subtracts, at each given time position, the meanof the time-resolved signals from the square of the standard deviationof the time-resolved signals to correct for shot noise.

At step 450, the integrated circuit 110 divides, at each given timeposition, the difference of the square of the standard deviation of thetime-resolved signals and the mean of the time-resolved signals by asquare of the mean of the time-resolved signals. The result of thisdivision is the time-resolved contrast. The procedure ends at step 460.While FIG. 4 depicts calculating the square of the standard deviationand the square of the mean, the integrated circuit 110 may alternativelycalculate the standard deviation and divide it by the mean. Further,while FIG. 4 shows calculations on the entire time-resolved signal, itis expressly contemplated that the calculations may be performed on asliding time window on each of the plurality of time-resolved signals.This may reduce the number of calculations required as described abovein reference to FIG. 3 .

FIG. 5 depicts various logical steps in method 500 for operating a LIDARsystem in a vehicle to overcome scattering effects in accordance with analternative embodiment of this invention. The procedure starts at step510 and moves on to step 520 where transmitter optics 102 coupled to thevehicle transmit light pulses at each of a plurality of locations in ascene to be scanned (e.g., N scanning locations). The LIDAR system 100may typically scan the scene in a raster scan so that each location isoriented at a pan angle and a tilt angle relative to the LIDAR system100 and so that locations in the vicinity of a given location can beeasily identified. The light pulses may originate from a light source101, including, but not limited to, a laser or an LED light source. Thelight pulses may be directed by transmitter optics 102 toward thelocation (e.g., one of the N scanning locations) in the scene. Thetransmitter optics 102 may alternatively spread the light pulses so asto flash-illuminate the whole scene.

The method proceeds to step 530 where receiver optics 109 coupled to thevehicle receive and detect light reflected from the scene in a timeperiod between light pulses. The receiver optics 109 thereby produces atime-resolved signal for each of the plurality of locations (e.g., eachone of the N scanning locations). Proceeding to step 540, the methodcalculates, by an integrated circuit 110, a time-resolved contrast overthe time-resolved signals produced for locations in the vicinity of aselected one of the plurality of locations. The integrated circuit 110may be an ASIC or a processor including program code. The integratedcircuit 110 may also be any other circuit configured to perform thecalculations. The calculations are described in further detail below inreference to FIG. 6 and are repeated for each one of the plurality oflocations (e.g., for each one of the N scanning locations).

The procedure then moves on to step 550 where the integrated circuit110, or another integrated circuit, generates a three-dimensional map ofthe scene from the calculated time-resolved contrast for each locationof the plurality of locations. The map may, for example, be generated bydetecting the time position of the absolute maximum or minimum of eachtime-resolved contrast. The time position at the maximum or minimumcorresponds to the distance to an object at the location in the scenecorresponding to that time-resolved contrast. At step 560, the generatedthree-dimensional map is utilized to affect the operation of thevehicle. The utilizing may comprise displaying the generated map on adisplay 111 superimposed on a visual image produced by a camera 113. Thesuperimposition 112 may aid a driver of the vehicle in recognizingobjects in front of the vehicle that would otherwise be invisible due tochallenging environmental conditions. For example, the superimposition112 may allow the driver to see an oncoming vehicle in dense fog. Theutilizing may further comprise using the generated three-dimensional mapto affect the operation of an autonomous vehicle as known to a personhaving skill in the art and, for example, contemplated in U.S. Pat. No.8,761,990. The procedure then ends at step 570.

FIG. 6 shows various logical steps in method 600 for calculatingtime-resolved contrast at a given location in accordance with analternative embodiment of this invention. The procedure starts at step610 and moves on to step 620 where the integrated circuit 110 calculatesa standard deviation at each given time position over the plurality oftime-resolved signals produced by the receiver optics 109 for locationsin the vicinity of the given location. At step 630, the integratedcircuit 110 calculates a mean at each given time position over theplurality of time-resolved signals produced for locations in thevicinity of the given location. The method proceeds to step 640 wherethe integrated circuit 110 divides, at each given time position, thestandard deviation by the mean. The result of this division is thetime-resolved contrast for the given location. The procedure ends atstep 650. While FIG. 6 depicts calculating the standard deviation andmean, the integrated circuit 110 may alternatively calculate the squareof the standard deviation and divide it by the square of the mean. Theintegrated circuit may also perform shot noise correction as describedabove in reference to FIG. 4 . Further, while FIG. 6 shows calculationson the entire time-resolved signal, it is expressly contemplated thatthe calculations may be performed on a sliding time window on each ofthe plurality of time-resolved signals to reduce the number ofcalculations required as described above in reference to FIG. 3 .

Embodiments of the invention may be implemented in part in anyconventional computer programming language such as VHDL, SystemC,Verilog, ASM, etc. Alternative embodiments of the invention may beimplemented as pre-programmed hardware elements, other relatedcomponents, or as a combination of hardware and software components.

Embodiments can be implemented in part as a computer program product foruse with a computer system. Such implementation may include a series ofcomputer instructions fixed either on a tangible medium , such as acomputer-readable medium (e.g., a diskette , CD-ROM , DVD-ROM, ROM, orfixed disk) or transmittable to a computer system via a modem or otherinterface device, such as a communications adapter connected to anetwork over a medium . The medium may be a tangible medium (e.g.,optical, digital, or analog communications lines) and the serious ofcomputer instructions embodies all or part of the functionalitypreviously described herein with respect to the system and methods.Those skilled in the art should appreciate that such computerinstructions can be written in a number of programming languages for usewith many computer architectures or operating systems. Furthermore, suchinstructions may be stored in any memory device, such as semiconductor,magnetic, optical, or other memory devices, and may be transmitted usingany communications technology, such as optical, infrared, microwave, orother transmission technologies. It is expected that such a computerprogram product may be distributed as a removable medium withaccompanying printed or electronic documentation (e.g., shrink-wrappedsoftware), preloaded with a computer system (e.g., on system ROM orfixed disk), or distributed from a server or electronic bulletin boardover the network (e.g., the Internet or World Wide Web). Someembodiments of the invention may be implemented as a combination of bothsoftware and hardware. Still other embodiments may be implemented asentirely hardware or entirely software.

The embodiments of the invention described above are intended to bemerely exemplary; numerous variations and modifications will be apparentto those skilled in the art. All such variations and modifications areintended to be within the scope of the present invention as defined inany appended claims.

What is claimed is:
 1. A light detection and ranging (LIDAR) systemcomprising: a source of light pulses; transmitter optics configured todirect a sequence of light pulses from the source toward a scene;receiver optics arranged to receive light reflected from the scene in atime period between light pulses and to provide a time-resolved signalof the reflected light produced by each of a plurality of the lightpulses; and an integrated circuit configured to calculate atime-resolved contrast over a time window of the plurality oftime-resolved signals, the time window corresponding to a time positionof the absolute maximum or minimum of the time-resolved contrast.
 2. TheLIDAR system of claim 1, wherein the time-resolved contrast correspondsto a standard deviation of the time-resolved signals at a given timeposition of the time window of the plurality of time-resolved signalsdivided by a mean of the time-resolved signals at the given timeposition of the time window of the plurality of time-resolved signals.3. The LIDAR system of claim 1, wherein the time-resolved contrastcorresponds to a difference of a square of a standard deviation oftime-resolved signals at a given time position of the time window of theplurality of time-resolved signals and a mean of the time-resolvedsignals at the given time position of the time window of the pluralityof time-resolved signals, the difference further divided by a square ofthe mean.
 4. The LIDAR system of claim 1, wherein the integrated circuitcomprises a processor including program code with instructions forcalculating the time-resolved contrast.
 5. The LIDAR system of claim 1,wherein the integrated circuit is an application-specific integratedcircuit (ASIC).
 6. The LIDAR system of claim 1, wherein the transmitteroptics are configured to spread the light pulses to flood-illuminate thescene.
 7. The LIDAR system of claim 1, wherein the source of lightpulses is a laser or a light-emitting diode (LED).
 8. The LIDAR systemof claim 1, further comprising a second integrated circuit configured togenerate a three-dimensional map of the scene from a plurality of thetime-resolved contrasts.
 9. The LIDAR system of claim 8, furthercomprising: a camera configured to produce a visual image of the scene;and a display configured to display the three-dimensional map of thescene superimposed on the visual image of the scene.
 10. The LIDARsystem of claim 1, wherein the integrated circuit is further configuredto generate a three-dimensional map of the scene from a plurality of thetime-resolved contrasts.
 11. A method for operating a LIDAR system in avehicle to overcome scattering effects, the method comprising: (a)transmitting, by transmitter optics, a sequence of light pulses towardsone of a plurality of locations in a scene to be scanned; (b) receiving,by receiver optics, light reflected from the scene in a time periodbetween light pulses to produce a time-resolved signal between each ofconsecutive light pulses; (c) calculating, by an integrated circuit, atime-resolved contrast over a time window of the plurality oftime-resolved signals produced by the plurality of light pulses, thetime window corresponding to a time position of the absolute maximum orminimum of the time-resolved contrast in the vicinity of the one of theplurality of locations; (d) repeating (a) through (c) for each of theremainder of the plurality of locations in the scene to be scanned; (e)generating a three-dimensional map of the scene from the plurality oftime-resolved contrasts for the plurality of locations; and (f)utilizing the three-dimensional map of the scene to affect operation ofthe vehicle.
 12. The method of claim 11, wherein the calculating furthercomprises: (i) calculating, by the integrated circuit, a standarddeviation of the plurality of time-resolved signals over the timewindow; (ii) calculating, by the integrated circuit, a mean of theplurality of time-resolved signals over the time window; and (iii)dividing, by the integrated circuit, over the time window, the standarddeviation by the mean.
 13. The method of claim 11, wherein thecalculating further comprises: (i) calculating, by the integratedcircuit, a square of a standard deviation of the plurality oftime-resolved signals over the time window; (ii) calculating, by theintegrated circuit, a mean of the plurality of time-resolved signalsover the time window; (iii) subtracting, by the integrated circuit, ateach given time position the mean of the plurality of time-resolvedsignals from the square of the standard deviation of the plurality oftime-resolved signals; and (iv) dividing, by the integrated circuit,over the time window, the difference of the square of the standarddeviation of the plurality of time-resolved signals and the mean of theplurality of time-resolved signals by a square of the mean of theplurality of time-resolved signals.
 14. The method of claim 13, whereα_(x) and α_(y), are angles corresponding to scanning of the LIDARsystem, σ(α_(x), α_(y)τ) is the standard deviation of the plurality oftime-resolved signals over the time window, μ(α_(x), α_(y), τ) is themean of the plurality of time-resolved signals over the time window, andK(τ) is a measure of angular and temporal speckle defined as σ(α_(x),α_(y), τ)/μ(α_(x), α_(y), τ).
 15. The method of claim 11, furthercomprising utilizing the three-dimensional map to detect an object inthe scene.
 16. The method of claim 11, wherein the transmitting furthercomprises spreading the light pulses to flood-illuminate the scene. 17.The method of claim 11, wherein the light pulses are laser pulses or LEDpulses.
 18. The method of claim 11, further comprising capturing, by acamera, a visual image of the scene and superimposing thethree-dimensional map of the scene on the visual image of the scene. 19.The method of claim 18, further comprising displaying thesuperimposition of the three-dimensional map of the scene and the visualimage of the scene to a driver of the vehicle.
 20. The method of claim11, wherein the vehicle is an autonomous vehicle.